The 61-kilometre line section between Innertkirchen and Mettlen is to be replaced and upgraded from 220 to 380 kilovolts. Swissgrid reviewed three planning territories for the line route: Glaubenberg (near the existing line), Pilatus (through the Sarneraa Valley) and Entlebuch (via Sörenberg and Entlebuch).
Most of the 61-kilometre extra-high-voltage line between Innertkirchen and Mettlen is over 70 years old and needs to be replaced. At the same time, the line voltage will be upgraded from the existing 220 kV to 380 kV along its entire length. This upgrade is an important project within Swissgrid’s implementation of «Strategic Grid 2025».
Expanding the amount of electricity produced from hydropower is a central pillar of the Energy Strategy 2050. The increase in capacity between Innertkirchen and Mettlen is necessary to be able to transport the growing volume of electricity generated by the Oberhasli power plants and the Valais and Ticino hydroelectric power plants to the Swiss Central Plateau. Distributing energy flows along several north-south axes also increases grid stability. The Innertkirchen – Mettlen grid project therefore not only supports the expansion of renewable hydropower, it also ensures Switzerland’s security of supply.
In mid-2021, Swissgrid applied to the Swiss Federal Office of Energy to establish a planning territory between Innertkirchen and Mettlen in the federal government’s sectoral plan for transmission lines. Planning territories are geographic areas within which a planning corridor, including transmission technology (underground cable, overhead line or combined options), can then be chosen at a subsequent stage of the project. To this end, Swissgrid examined three partly overlapping planning territories.
Both of the submitted variants have specific advantages and disadvantages with respect to regional planning, the environment, technology and economic viability. From Swissgrid’s perspective, the Glaubenberg planning territory provides is the best of the three options. Firstly, it touches fewer settlement areas and involves fewer obstacles than the other options. Secondly, it is much shorter than the planning territory via Entlebuch and so has less of an impact on the ground, the natural environment and the landscape, requires less construction material and has lower energy losses and costs.
The section between Mettlen and Hellbühl (Littau) is considered separately. It was upgraded to 380 kV in 1990, but is currently operating at just 220 kV. The Innertkirchen – Mettlen and Bickigen – Mettlen lines approach one another to the west of Rothenburg, from where they are bundled in the section to Mettlen. With this in mind, it makes sense to consider both lines together in this section in order to provide permanent relief for the settlement area. Swissgrid will therefore review the line routing in this area as part of the planned Bickigen – Mettlen line renovation. The line lead-in for the Innertkirchen substation will be considered separately within the Innertkirchen – Mettlen sectoral plan process: two additional transmission lines run parallel to the Innertkirchen – Mettlen line along a roughly two-kilometre section. As all three lines pass through the settlement area, the only option in this section is to install an underground cable in a tunnel.
In the next stage of the sectoral plan process, a monitoring group appointed by the Swiss Federal Office of Energy (SFOE) will come together with the federal authorities, the affected cantons and environmental associations to discuss and assess the planning territory options developed by Swissgrid. The monitoring group’s recommendation will then be taken forward to the public consultation stage. The Federal Council is expected to decide on the planning territory between Innertkirchen and Mettlen by autumn 2023. Swissgrid will then set out various planning corridors for each transmission technology (overhead line, underground cable or combined versions) within this planning territory and submit these to the SFOE monitoring group. The corridor will then be stipulated by the Federal Council. Ideally, the renewal of the Innertkirchen – Mettlen extra-high-voltage grid will be completed by 2035. After that, the existing line, parts of which run through the settlement area, will be removed.
